# `registry-augmentation.ts` — `ServiceRegistry` slot for `eventBusService`

## Purpose

Augments `@suaveplan/api-plugin/service-registry`'s `ServiceRegistry`
interface to advertise the `eventBusService` slot the plugin
registers at boot. Downstream plugins typed against the augmented
registry see `ctx.getService("eventBusService")` resolve to
`EventBusService | undefined` without any cast. Mirrors the pattern
used by `@suaveplan/api-plugin-auth`'s `registry-augmentation.ts`.

The module re-declares the host-side slots (`app`, `openAPIRegistry`,
`logger`, `eventBus`, `clock`) as a cumulative augmentation so the
plugin's `onInit(ctx)` can resolve them with full typing even when the
consumer has not separately imported `@suaveplan/api`. TypeScript
merges duplicate `interface ServiceRegistry { ... }` declarations, so
the duplication is safe alongside `@suaveplan/api`'s own
augmentation.

## Features

- Side-effect-only module — importing it surfaces the augmentation to
  every consumer.
- Re-declares the host-owned slots so the plugin compiles in
  isolation.
- Marks `openAPIRegistry` as optional — the plugin tolerates a host
  that does not register an OpenAPI registry by mounting routes on
  the Hono app only.

## Usage: Basic

```ts
import "@suaveplan/api-plugin-event-bus/services/registry-augmentation";

// elsewhere — typed without any cast
const bus = ctx.getService("eventBusService");
```

## Usage: Advanced

```ts
import type { EventBusService } from "@suaveplan/api-plugin-event-bus";
import "@suaveplan/api-plugin-event-bus/services/registry-augmentation";

function consume(getService: <K extends string>(name: K) => unknown) {
    // Augmentation makes the literal "eventBusService" resolve
    // cleanly against the registry interface.
    return getService("eventBusService") as EventBusService | undefined;
}
```

## API Reference

This module exports nothing at runtime. The declaration:

```ts
declare module "@suaveplan/api-plugin/service-registry" {
    interface ServiceRegistry {
        eventBusService: EventBusService;
        app: OpenAPIHono;
        openAPIRegistry?: OpenAPIRegistry;
        logger: LoggerLike;
        eventBus: EventBusLike;
        clock: Clock;
    }
}
```

is the entire surface.

## Implementation Notes

- An empty `export {};` keeps the file in module scope — TypeScript
  treats files with only `declare` statements as scripts otherwise.
- The host-owned re-declarations match the canonical slot names used
  in `@suaveplan/api`'s own augmentation. If those slot names change
  upstream, this file must follow.
- `openAPIRegistry?: OpenAPIRegistry` differs from `@suaveplan/api`'s
  required declaration on purpose — the event-bus plugin tolerates
  hosts without OpenAPI by mounting routes on the Hono app alone.
  TypeScript's module-merging treats the optional declaration as a
  widening, so consumers importing both modules still see the
  required form.